This Design Note describes an up to 10 watt, off-line universal input, LED string driver with power factor correction (PFC). It incorporates a revised version of the NCP1014 “mini” boost power factor corrector circuit described in ON Semiconductor Design Note DN06064 in conjunction with ON Semiconductor’s new NSI45025 series constant current regulator.This latter device is a 2-pin part which can be inserted in series with a string of LEDs and provide a highly stable constant current and withstand a compliance voltage from 2 to 45 volts.